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Pulse Generators "Stimulate" Medical Device Industry
Increasing the feedthroughs is a concern for the advancement of IPGs for medical applications.
By Chris Vaillancourt, Business Unit Manager for Medical Products, Morgan Technical Ceramics
Neuromodulation has spurred a great deal of excitement in recent years for treatment of different medical conditions and diseases. This technology uses electrical signals to stimulate or block different nerve impulses in the body and is adapted from technology used in cardiac rhythm management. It holds promise for a variety of conditions, including reducing or eliminating back pain, curing obesity, lowering high blood pressure, and controlling diabetes without daily injections of insulin.
Advanced ceramic materials are playing an important role in the technology and are poised to play an even greater one as these medical devices treat an increasing number of ailments. Ceramic-to-metal brazed assemblies for hermetically sealed electrical feedthroughs, piezocomposite materials that facilitate ultrasonic device communication, and biocompatible ceramics as an alternative to titanium device casings are just a few of the ways that advanced ceramics are playing a part in enhancing this technology. These ceramic materials and technologies play an important part in developing new and innovative treatment methods that were simply not possible with traditional materials.
Research and development on new ceramic composite materials and assemblies, as well as high-pin-density feedthrough assemblies, are being pursued to enable a next generation of neuromodulation devices that will provide better treatment, improved patient safety and convenience, and better communication with other devices.
Central to the technology is a neurostimulator, usually referred to as an implantable pulse generator (IPG). The IPG is a battery-powered microelectronic device, implanted in the body, which delivers electrical stimulation to the nervous system. An essential part of surgically implanted systems designed to treat a wide array of conditions, the IPG delivers very small pulses of electricity to block or stimulate nerve signals (or impulses), depending upon the condition.
A variety of different electrical feedthroughs are laser-welded to an IPG case. They provide reliable transport of electrical signals from the IPG electronics hermetically sealed inside the case to the nerve locations that effect treatment. In some cases, the devices are used where medicines have not been completely effective, or have unpleasant side effects. In other cases, nerve stimulation may control a condition more conveniently for the patient, either alone, or in combination with medicine. The payoff would be significant if a device could be implanted in the body laparoscopically, with only a very small incision. The thought of a short, 20-minute outpatient surgery followed by years of 100 percent patient compliance and possibly eliminating medicine has doctors, patients, and insurance companies very excited.
The feedthrough, the mechanical structure that provides electrical connections for leads into and out of the device housing, is a key component of these IPG devices. This tiny component performs several key functions. First, it provides the conduit for communication of signals between the IPG and the body. Second, its hermetic seal keeps body fluids outside the IPG device and prevents electricity and battery materials from leaking into the body. The feedthrough must be completely and totally leak-free, and robust enough to withstand radio frequency interference (RFI) and eliminate interference from MRI equipment and anti-theft scanners. This tiny piece of device real estate can contain as few as 2 leads and as many as 30 leads.
Morgan Technical Ceramics — Alberox (MTC-Alberox) specializes in the customization of feedthroughs, providing design assistance and often working through several design iterations with a device designer before arriving at an optimized feedthrough design for a device. According to John Antalek, MTC-Alberox's Medical Unit Business Manager, "The feedthrough technology is changing rapidly, as next generation devices get smaller and more compact and device designers seek to add more leads to improve the therapeutic value of the devices."
Antalek says that many device manufacturers often start with an off-the-shelf feedthrough to get their first-generation device on the market. Their next-generation devices are much smaller and more compact, which makes them more acceptable to doctors and patients. The new generation also tends to have many more bells and whistles, and customers come to MTC to obtain a customized feedthrough that incorporates the additional features needed. "Since we make our ceramic components in house, we have developed manufacturing processes capable of producing numerous sizes and shapes of feedthroughs to match the device design needs."
New IPG Uses
New medical uses for IPG devices are patented frequently. Among the conditions for which the devices show the most promise are chronic back pain, hypertension, and diabetes. Examples of devices focused on these conditions (either available now or under investigation) are provided below. IPG devices deliver mild electrical pulses to the spinal cord, which interrupt or mask the transmission of pain signals to the brain. In this application, the IPG is implanted in the back, in close proximity to the nerve that doctors are trying to block.
Most patients with high blood pressure control the condition by using a regimen of anti-hypertensive drugs. However, many studies have reported a persistence of refractive hypertension (elevated blood pressure despite using at least two anti-hypertensive drugs) in as many as 18 percent of the patient population. IPG devices are being developed to provide a new and improved therapy for treating hypertension that is not only safe and effective, but avoids undesirable side effects of drug therapy. The system includes an IPG, sensors and leads, external electronics for calibration, programming, and periodic adjustment of parameters by the attending physician.
Several devices are being used or are under development, especially as an option for patients with diabetes who have not been responsive to drug therapy. An IPG is implanted and used to stimulate or inhibit the patient's vagus nerve to modulate its electrical activity to increase or decrease secretion of natural insulin by the patient's pancreas. The stimulator might be selectively activated in response to direct measurement of blood glucose or symptoms, or could be activated automatically at predetermined times or intervals. Alternatively, it could be automatically activated using an implanted sensor to detect blood glucose concentrations.
The general trend in implantable devices is miniaturization. New devices tend to be smaller, but with a greater number of leads to transfer more signals into and out of a single device. Improving the feedthrough and expanding its capability are central to the next generation of IPGs. Future neurostimulator applications are currently looking at 100 to 200 leads, which will give device manufacturers opportunities to add further treatment to an implantable system. MTC-Alberox's John Antalek notes: "We know where the IPG device is headed and we want to proactively provide improved feedthrough capabilities to help the device manufacturers meet their needs." He adds: "Just look at how far we've come with cardiac rhythm management. Pacemakers were the size of a Blackberry just a few years ago and had only two leads. Now the typical pacemaker is about the size of a lighter and can have as many as 10 leads, some of which allow better communication to the device, monitoring of other patient information, and the ability to send information directly from the device to a doctor." Additional leads could also build in intentional redundancy, which would reduce the device downtime and eliminate the need to remove the device if any of the leads fail.
One of the most exciting avenues of research to increase the number of leads is the development of new high-density feedthroughs that could contain ten times the number of leads with the current size and spacing. Today's feedthroughs are constructed by assembling many different parts, stacking them into complicated arrays with braze materials, and putting them into a furnace for joining. However, researchers are now developing high-density feedthroughs using cutting-edge advanced ceramic materials and processing technologies that use miniaturization techniques to pack many more wires together in a much tighter space.
The market for neuromodulation is estimated at more than $2 billion, with a compound annual growth rate (CAGR) estimated at 18-22 percent and a seemingly never-ending supply of new applications for the basic technology. With an increasing acceptance by the Food and Drug Administration and insurance companies, preference over some drug therapies, and increasing device complexity to deliver more features and more tailored effects, developing the next generation of IPGs is critical to the advancement of neuromodulation technology.
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